The goal of affording computer users the ability to print, fax or otherwise output document, image or other output exactly as they see the content on screen has been a perennial but elusive one. While the objective of what-you-see-is-what-you-get (WYSIWYG) output has been pursued in the marketplace for some time, obstacles to truly consistent screen-to-print and other output remain.
The difficulty in generating consistent output is in part related to the differing approaches used to try to unify the depiction of documents, graphic images and other output representations. On the one hand, the approach can be taken that an output representation on the user's screen should be conformed to the output characteristics of the target printer or other output device. This approach is exemplified for instance by the Display PostScript™ system, a display rendering platform which attempts to limit and match the rendering functionality on the desktop to that which is provided by target printers or other devices. This may severely constrain the available output on an average CRT or LCD display, which may be able to render to much higher color or grayscale resolution, for example, than a printer.
Conversely, the approach can be taken to try to emulate or conform the output characteristics of a printer, fax or other output device to the same characteristics as the computer desktop display, as for example generally illustrated in FIG. 1. This approach may be typified for example by the use of the Graphic Device Interface (GDI) dynamic link libraries (DLLs) to drive print or other output operations. However among other drawbacks GDI technology may impose a performance penalty on printed or other output.
When either the desktop screen or the output device attempt to emulate the other, complications may also arise in other ways. Those difficulties can result in part from the fact that the output characteristics, such as resolution, color depth and others, of the desktop or other source screen rarely if ever match or even approximate the output characteristics of the printer or other output device. Therefore perfectly accurate emulation by one device of the other may be difficult or impossible, even in principle.
Compounding the mismatch between the two sides of the hardware, the display driver for the desktop screen and the device driver for the printer may moreover not be one in the same software. The device-specific drivers for the display and for the printer may take different approaches and make different assumptions about how a graphical object may be represented and ultimately rendered, for example implementing operations such as halftoning, interpolation, kerning and other effects differently. A preview of print output on the user's screen may therefore show an accurate representation of what the video display system will generate for the document or other content, but not for the printer, facsimile or other output device. Other problems in document and other graphical output technology exist.